Differential regulation of the expression of cytochrome P450 aromatase, estrogen and androgen receptor subtypes in the brain–pituitary–ovarian axis of the Japanese eel (Anguilla japonica) reveals steroid dependent and independent mechanisms

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…In the Japanese female eel, E2 treatment induces an up regulation of ESR1 but not of ESR2 (Jeng et al, 2012b). ).…”

“…These two genes have been identified in many fish species, including the Nile tilapia Oreochromis niloticus , the zebrafish Danio rerio (Trant et al, 2001), the goldfish Carassius auratus (Callard et al, 1997); the Chinese rare minnow Gobiocypris rarus (Wang et al, 2010); the atlantic halibut, Hippoglossus hippoglossus (van Nes et al, 2005), the rainbow trout Oncorhynchus mykiss (Tanaka et al, 1992;Valle et al, 2002); the European sea bass Dicentrarchus labrax (Blazquez and Piferrer, 2004), the orange-spotted grouper, Epinephelus coioides (Zhang et al, 2004)and the ricefield eel, Monopterus albus . Nevertheless, only a single copy of P450 aromatase has been identified in the eel (called cyp19a1) and it is expressed in the ovary, brain and pituitary Jeng et al, 2012b;Peñaranda et al, 2014).…”

“…These results again suggest a differential regulation of the nuclear estrogen receptors during the maturation of male and female eels. According to Jeng et al (2012b), E2 plasma levels may up-regulate the expression of ESR1 in the brain of female Japanese eel. As E2 plasma levels decreased throughout spermatogenesis in male eels, the expression of ESRs does not seem to respond to a peripheral E2 production but rather to a local production in the brain.…”

“…These two genes have been identified in many fish species, including the Nile tilapia Oreochromis niloticus , the zebrafish Danio rerio (Trant et al, 2001), the goldfish Carassius auratus (Callard et al, 1997); the Chinese rare minnow Gobiocypris rarus (Wang et al, 2010); the atlantic halibut, Hippoglossus hippoglossus (van Nes et al, 2005), the rainbow trout Oncorhynchus mykiss (Tanaka et al, 1992;Valle et al, 2002); the European sea bass Dicentrarchus labrax (Blazquez and Piferrer, 2004), the orange-spotted grouper, Epinephelus coioides (Zhang et al, 2004)and the ricefield eel, Monopterus albus . Nevertheless, only a single copy of P450 aromatase has been identified in the eel (called cyp19a1) and it is expressed in the ovary, brain and pituitary Jeng et al, 2012b;Peñaranda et al, 2014).Estradiol (E2) is derived from the aromatization of T into 17b-estradiol (fig 4) or from androstenedione into estrone and further into estradiol. Estrogens are known to be involved in the regulation of oogenesis, spermatogenesis, vitellogenesis, gonadotro-pin regulation, and other aspects of reproduction, in addition to the pleiotropic effects they have on many target organs such as the gonads, the cardiovascular system, the liver, the skeleton, and the nervous system (Bazer et al, GENERAL INTRODUCTION 21 2010;Heldring et al, 2007;Hess, 2003;Horner, 2009;Matthews and Gustafsson, 2003;Nilsson et al, 2001;Nagler et al, 2012;Pang and Thomas, 2009;Shi et al, 2013; for review see Nelson and Habibi, 2013).…”

Effect of thermal regime on the expression of key reproductive genes during hormonally-induced vitellogenesis in female European eels

“…These steroid immunoassays were previously carried out on the eels to measure the increases in androgen plasma levels during the transition from the juvenile yellow stage to the prepubertal silver stage (silvering; , and during experimental maturation (Peñaranda et al, 2010;Jeng et al, 2012).…”